The food, pharmaceutical and cosmetics industries have focused their efforts on searching for new economically viable production processes with moderate thermal treatments. Examples of these new production processes are the use of emerging technologies, such as the application of high pressure and the application of ultrasounds, and, in turn, the use of each of these two technologies combined with thermal treatments. On the other hand, flash vacuum expansion is a process in which the materials are heated with steam and are then immediately introduced in a vacuum chamber where they expand and break down, producing flash evaporation of a portion of the water contained in plant tissues and aromatic volatile components.
This invention is based on forming an apparatus in which the technologies of flash vacuum expansion and simultaneous treatment with ultrasounds are combined for various applications in the food, pharmaceutical and cosmetics industries.
In recent years the food, pharmaceutical and cosmetics industries have focused their efforts on searching for new economically viable production processes for the purpose of meeting constant consumer demand for novel, safe and non-perishable products (Señorans et al., 2003). Examples of these new production processes are the use of emerging technologies, such as the application of high pressure and the application of ultrasounds, and in turn, the use of each of these two technologies combined with moderate thermal treatments (Earnshaw 1996; Butz, Fernández García et al., 2003; Knorr et al., 2004; Urrutia-Benet et al., 2004; Ashokkumar et al., 2008).
Flash vacuum expansion is a process in which plant materials are heated at 60-90° C. with steam and are then immediately introduced in a vacuum chamber (2.10−3 to 1.10−2 MPa) where they expand and break down due to the formation of microchannels within the tissues. Flash evaporation of a portion of the water contained in the constitutive plant tissues and aromatic volatile components takes place in this process. This evaporation process in turn produces cooling in the plant tissue, which produces a structural disruption, and accordingly accelerates the phenomenon of diffusion or maceration of the components thereof (Brat, 2001).
Different pieces of equipment have developed technologies in which flash vacuum expansion is applied.
Patent document WO2006/024762 A1 discloses a process of cooling at reduced pressure including the installation for implementing same. The method consists of an installation for cooling plants from temperature T1 to a lower temperature T3, in which the plants at temperature T1 are subjected to reduced pressure to partially vaporize the water contained therein and to cool said plants to temperature T3. Fractional cooling takes place: a first step cools the plants from temperature T1 to intermediate temperature T2, carrying out a first vaporization in a first cooling chamber under absolute reduced pressure P1; a second step consisting of cooling said plants from temperature T2 to T3, involving a second vaporization in a second cooling chamber under absolute reduced pressure P2, and said plants end up at temperature T3 which is less than 30° C. and preferably less than 28° C. after the second cooling step (Merican, 2006)
Another system for cooling a hot juice by partial, low-pressure evaporation is disclosed in patent document WO 02/096530 A2. A hot juice is subjected to several pressure reductions in at least two different compartments which communicate with each another by means of a pulsed-effect valve. The juice is subjected to two different pressure reductions in said compartments, each compartment being communicated with a condenser which condenses the vapor produced by the pressure reduction. The serially or parallel mounted condensers are connected to a vacuum pump by means of a control valve which can permanently adjust the pressure in each condenser to a value which is lower than the saturated vapor pressure corresponding to the temperature of the generated vapor. The invention is characterized in that the compartments are superposed and communicate with each other therein by means of an opening through which the juice passes, said position being open or closed either fully or partially by a variably positioned shutter element, creating a pulsed effect to remove the solid particles contained in the juice. (Nadeau, 2002).
French patent document 2813010 discloses a process for manufacturing a pectin-rich citric extract using the low-pressure method as follows: the flavedo is removed by means of scraping, the fruit is heated at a temperature of less than 110° C., and the hot citrus is subjected to reduced pressure for less than 3 seconds. A pulp-rich product that can be used to obtain soluble pectin-rich extract is finally obtained.
Patent document EP0727948 (A1) relates to processing hydrated plant materials, specifically for the extraction of juice and flavor from various substrates such as fruit, vegetables or leaves. It specifically relates to an installation in which it is unnecessary to add exogenous water to heat or bleach said materials. It is a continuously operating installation consisting of a heating chamber, a decompression and vaporization chamber connected to the heating chamber and to a condenser which is in turn connected to a vacuum pump (Cogat, 1996).
This technology is based on the developments described in patent document U.S. Pat. No. 3,293,046 of Werther (1966), French patent document 263833 of Cogat, Hunez and Pieribattesti (1988), and French patent document 2656547 of Cogat (1989).
This technology has given rise to multiple applications. The applications of flash expansion technology are specifically described below.
Flash vacuum expansion has been used in obtaining volatile compounds from passion fruit purée. The vapor heating process provides a purée with a higher concentration of total volatile compounds, particularly esters, compared to a reference purée due to the incorporation in the purée of part of the peel. After expansion in a vacuum, the purée is depleted of volatile components due to the flash evaporation of water when the fruits are introduced in the vacuum chamber. Most of these volatile compounds are recovered in the aromatic liquors generated by going through the expansion vacuum, and these could be added to the purée (Brat et al., 2000). Also by means of applying flash expansion to a purple passion fruit purée an intermediate product is obtained that is somewhere between a juice and a purée, giving rise to a new food product, with an output that exceeds that of the process for conventionally obtaining such products by two-fold. The high viscosity of the mash is closely related to its content of starch-free alcohol-insoluble residues (Brat, 2001).
Compared to conventional techniques, the method of treating grapes before wine fermentation by means of flash expansion technology provided a pronounced increase in the amount of pigments. The amount of total phenols can be 50% greater than that found in control wines. This increase in the polyphenol content is stable for years. Total dry weight increased up to a maximum of 30 g/L. The wines thus produced are less susceptible to oxidative deterioration (Moutounet and Escudier 2000).
Treating grapes by means of flash expansion (FE) technology also results in musts and juices enriched with all types of phenolic compounds. However, the concentration thereof decreases drastically throughout fermentation when a pressing treatment is applied after flash expansion. Wines obtained after fermenting musts treated using flash expansion have a higher concentration of flavonoids, catechins, anthocyanins and proanthocyanidins than control wines and slightly lower amounts of hydroxycinnamic acids. Keeping the grapes at a high temperature before FE treatment also increases the degree of phenolic compound extraction. On the other hand, high-temperature treatment also increases reactivity of phenolic compounds, and particularly conversion of anthocyanins into pigments showing more colors. FE increases the tannin-anthocyanin ratio and the formation of tannin-anthocyanin complexes favoring wine color stability (Morel-Salmi et al., 2006).
Flash vacuum expansion technology applied to lemon, orange, grapefruit and mandarin peels (heating with vapor followed by quickly going through a vacuum tank) allows obtaining essential oils by means of coupling a condenser and then separating them in a centrifuge. Obtained outputs were 2.41, 1.43, 0.64 and 0.73 k/ton of fruit for lemon, orange, mandarin and grapefruit, respectively. The obtained oils were enriched in limonene and other monoterpenes. The relative amounts of monoterpenes (linalool, alpha terpineol, beta citronellol, nerol, geraniol) and aldehydes (neral, geranial) were lower compared to the initial values initially obtained from the peel. The values of essential oils obtained from citrus peels by applying flash expansion are comparable to those obtained with FMC inline extractors when processing these citrus fruits. The obtained oils were rich in monoterpenes and correlatively depleted of volatile oxygenated constituents (Brat et al., 2001).
Another alternative technology with future prospects in the food, pharmaceutical and cosmetics industries is the use of high-intensity ultrasounds. Ultrasonic waves convert electric energy into mechanical vibration which in turn causes intense agitation of the molecule in the treated medium. Many specific ultrasound mechanisms are still unknown, but it has been demonstrated that most of them can be related to processes such as cavitation (formation of bubbles and the violent collapse thereof), heating (specific acoustic energy absorption), dynamic agitation, turbulence (micro-streams), and others. Large-amplitude waves (10 kHz-1 MHz) are generally the most suitable for applications such as cleaning, drilling, emulsification, welding, therapeutic uses, and chemical and biological applications. On the other hand, the low-amplitude waves are more effective for applications such as security systems, medical instrumentation, and material testing. In preparing foods, ultrasounds can be applied to cleaning, emulsifying, mixing, alcohol fermenting, extracting, cutting, drying, spraying, degassing and cell disruption (Koo Min et al., 2002).
Ultrasound technology is the result of the discovery of the piezoelectric effect by the Curies in 1880. Most ultrasound apparatus today are equipped with transducers that are based on this effect and convert electrical signals into mechanical signals, and vice versa. Most of the developments being made today focus on the design of this equipment and the design of electronic and computer circuits, taking into account understanding of the phenomenon of cavitation and its impact. Therefore, high-frequency alternating current can be converted into ultrasonic waves by means of an ultrasonic transducer (Mason, 1998). These waves can be amplified and applied by means of an ultrasound probe or an ultrasound bath. This probe can in turn be submerged in a liquid medium to be treated, or in the case of the bath, said bath is filled with the liquid to be treated. The antimicrobial effect of ultrasounds is due to cavitation, i.e., the extremely rapid formation and subsequent collapse of bubbles formed by ultrasonic waves in a medium (Earnshaw, 1998). Cavitation causes local changes in pressure and temperature, which causes break down of cell walls, disruption and thinning of cell membranes, and DNA damage by means of free radical production (Earnshaw et al., 1995; Sala et al., 1995).
There are different developments based on this technology. The combination of treatment with ultrasounds and high pressure leads to microbial inactivation. Ultrasounds do not have a strong lethal effect on microorganisms at ambient temperature and pressure (Raso et al., 1998; Pagan et al., 1999). High treatment intensities can cause microbial inactivation, but at the same time they cause adverse sensory changes in foods (Sala et al., 1995). A milder but effective treatment is called manosonication (MS). This treatment uses moderate doses of ultrasounds under slight pressure. In turn, manothermosonication (MTS) describes a manosonication process carried out at high temperatures (Hayden, 1991; Ordoñez et al., 1992; and Williams 1994). Raso et al. (Raso, Pagan et al., 1998) studied Y. enterocolitica inactivation by means of the combination of ultrasounds, pressure and heat. The lethal effect of ultrasounds (20 kHz, 150 Am) increased with the progressive increase in pressure until reaching an optimum value of 400 kPa. Levels of destruction of B. subtilis spores with MTS (20 kHz, 117 Am) followed a similar trend under increasing pressure, with maximum inactivation at a pressure of 500 kPa (Raso et al., 1998b). Pagan et al. (1999) also demonstrated L. monocytogenes inactivation by applying ultrasound (20 kHz, 117 Am). This inactivation increases drastically when pressure increases from ambient pressure to 200 kPa. However, the increase in the rate of inactivation became increasingly smaller over time, when pressure values went up from 200 to 400 kPa. The authors theorized that the higher lethal effect of ultrasounds with moderate pressure was due to the higher intensity of cavitation. It should be clarified that pressures applied during manosonication (for example, 200-600 kPa) are not within the lethal scope of pressures applied during high-pressure treatment (for example, 50-1000 MPa; Williams, 1994). Sala et al. (1995) demonstrated that the lethal effect of MTS treatments for bacterial cells, spores and fungi was 6.30-fold greater than thermal treatments that do not apply ultrasound and pressure, and they concluded that the combined effects of ultrasounds, pressure and heat were synergistic. Raso et al. (1998) and Pagan et al. (1999) also indicated that microbial inactivation increased when MS was combined with temperatures exceeding 50° C. However, the lethal effect of MS combined with heat gave only an additive, not synergistic, effect, which seems to be because both treatments act by means of two different and independent mechanisms, unlike the synergy between ultrasound and pressure.
Pagan et al. (1999) found that the effect of treating Listeria monocytogenes with ultrasound (20 kHz, 117 Am) under sub-lethal pressure levels (200 kPa) was not affected by a drop in pH from 7 to 4. Acidity conditions have a much greater effect on resistance of the organism to heat than on sensitivity thereof to ultrasounds. Similar findings were reported long before that by Kinsloe et al. (1954), who exposed bacterial and yeast cells to a sound field in saline suspensions of a different pH. The pH dropping from neutral to 4.0 did not affect mortality rates of Pseudomonas aeruginosa or Saccharomyces cerevisiae in ultrasounds. For E. coli, Serratia marcescens and Micrococcus varians, higher mortality rates were only observed when the treatment temperature was greater than 45° C. and treatment was combined with ultrasounds and lower values of pH (Kinsloe et al., 1954).
The combination of treatment with ultrasounds and antimicrobial agents is also effective. Arce-García et al. (2002) were able to reduce the intensity and duration of treatment with ultrasound necessary for inhibiting Zygosaccharomyces rouxii by 67% and 33%, respectively, by means of incorporating potassium sorbate, sodium benzoate or eugenol in the recovery medium. The authors suggest that the different modes of action of ultrasounds, mild heating (45° C.) and antimicrobial hurdles were responsible for the observed inhibition. Ahmed and Russell (1975) found that the combination of ultrasounds and hydrogen peroxide was much more lethal for Bacillus and Clostridium spores than any individually applied treatment. These authors postulated that the ultrasonic waves improve the lethal effect of hydrogen peroxide by means of an increase in cell permeability, increasing the rate of reaction between the hydrogen peroxide and cell components, and dispersion of cells aggregates, resulting in an increase in contact surface (Ross et al., 2003).
In summary, the description from the prior art of these technologies allows establishing the following.
Effect of ultrasounds: Although thermal treatment continues to be the most widely used pasteurization technique, there is growing interest in developing alternative preservation techniques causing minimal changes in organoleptic and nutritional properties. Non-thermal processing techniques that show potential include electric or magnetic fields, ionizing radiations, white light pulses, high hydrostatic pressures and use of ultrasounds. Ultrasounds have been identified as technology having enormous potential for meeting US Food and Drug Administration (FDA) requirements of a log reduction of 5 in survival of pertinent microorganisms that can be found in fruit juices. When high-power ultrasounds are propagated in a liquid, cavitation bubbles are formed due to intense changes in pressure. These microbubbles violently collapse in successive compression/vacuum cycles propagated in the sound wave, forming a cavitation series having intense destructive effects. There are several studies on the effects of ultrasounds in microbial inactivation of fruit juices.
Effect of the flash expansion process: during this treatment, the material to be treated is subjected to a mild heating process, such that the water contained inside the cells and structures increases in temperature, and when it is suddenly introduced in a high vacuum container, this temperature is enough to cause the immediate change from the liquid to the vapor state, causing the cells and structures to burst. The microorganisms can logically also be included during cell structure bursting, the material thereby being sterilized. This theoretical situation is distorted by the protective effect that certain plant structures have on the microorganism and prevent full effectiveness of this principle.
Hence the object of this invention; by introducing the impact of the series of ultrasonic bubbles at exactly the same time as the material is subjected to flash vacuum expansion, increasing the destructuring of the material and facilitating access of the vacuum to cell structures and the impact on the microorganisms.
The accumulated experience of the group of inventors based on different experiments that have been previously conducted (assays with the company Electricité de France (EDF), R&D with orange juice and ultrasound equipment that allowed pasteurizing juice with thermal treatments at a low temperature (50° C.) [Effects of ultrasonic treatments in orange juice processing. M. Valero, N. Recrosio, D. Saura, N. Muñoz, N. Martí, V. Lizama. Journal of Food Engineering 80 (2007) 509-516] but with very long processing times. Assays with flash expansion equipment on a semi-industrial level (1000 kg/hr), and with pilot glass equipment suitable for processing 10-20 kg/h) led to considering the designs and construction of equipment which will complement both actions. Equipment that can provide ultrasound treatment, while at the same time subjecting the material to be treated to continuous flash vacuum expansion, has been designed and constructed.